Combined Dietary Effects of Tenebrio molitor Meal and Probiotics on Growth Performance, Immune Response, and Pathogen Resistance in Nile Tilapia (Oreochromis niloticus)

Abstract

The prospective utilization of insects as alternative protein sources to replace fishmeal (FM) in aquafeed has prompted increased interest. This study evaluated the effects of yellow mealworm Tenebrio molitor (TML)-based diet supplemented with 2% mixed probiotics on growth performance and resistance to Aeromonas hydrophila infection in Nile tilapia (Oreochromis niloticus). Six experimental diets were formulated. The control group (CTRL) received commercial feed containing 30% FM. In the experimental groups (T25P⁺, T50P⁺, and T100P⁺), FM was replaced with TML at inclusion rates of 25%, 50%, and 100%, respectively. The T50P^– group was identical to the T50P⁺ group but lacked probiotics, whereas the CTRLP⁺ group received the control diet (without TML) supplemented with 2% probiotics. Juvenile tilapia weighing 12.81 ± 1.37 g were fed the respective diets for 8 weeks. By the end of the feeding trial, fish receiving the T50P⁺ diet exhibited superior overall performance, characterized by a significantly higher weight gain (WG; 91%) and survival rate (98%) compared with the CTRL (p < 0.05). This group also demonstrated markedly enhanced digestive enzyme activities, including protease (30.5–34.7 U/mg), lipase (18.2–22.6 U/mg), and amylase (20.8–23.5 U/mg), alongside elevated lysozyme activity, improved antioxidant capacity, and stronger bactericidal activity. Although the T100P⁺ diet led to improvements in several parameters relative to the control, its overall performance remained inferior to that of the T50P⁺ group, indicating that partial replacement of FM was more effective than complete substitution. Furthermore, fish fed the T50P⁺ diet displayed enhanced fillet quality, evidenced by higher crude protein (CP) content (59.63%) and a moderate lipid level (29.73%). Following challenge with Aeromonas hydrophila, the T50P⁺ group showed a substantially reduced mortality rate (20%) compared with the CTRL (80%), confirming a pronounced improvement in disease resistance. Overall, the results suggest that replacing 50% of FM with TML in combination with probiotics enhances growth, nutrient utilization, immune function, and pathogen resistance in Nile tilapia. This TML–probiotic formulation represents a promising, sustainable, and effective alternative to conventional aquafeeds.